Mabel Cooper's Life Story Essay Example | Topics and Well Written Essays - 1500 words

Mabel Cooper's Life Story - Essay Example ‘Mabel Cooper’s Life Story’ is a heroic tale of a very determined individual who survived in society against all odds. Qs. 1. Discrimination and stigmatization that Mabel encountered during her life Mabel was born to a poor and homeless mother on the 10th of August, 1944 in Islington, London, but was moved into care when she was just four months old. Thereafter, her childhood was spent in different care schools and finally she was moved to St. Lawrence Hospital, Surrey, where she spent the next 20 years of her life. Mabel was discriminated and stigmatized because she had a learning disability and had never been to school and moreover she had a very poor background history. Mabel was told that she was not capable enough to study and so was put in a ward where they learned basket making. They also had the option of working in the laundry or workshops or even remain idle if they wished. A learning disability proved to be a real setback for Mabel and besides not being allowed to go to school, she was also not allowed to use her own clothes or shoes but had to make do with the ones given by the hospital. Though dances were conducted on the premises, they were again segregated with males on one side and females on the other. There were a good number of staff and they had to dance in between them. Mabel and her friends were discriminated from society by not being allowed to go out and mix with the regular people. Money in the form of green coins were given to them but it could only be used in their own hospital canteens and not outside. People who ran away were brought back and put in a ward called G3 where they were locked up as punishment. In this manner people with learning disabilities were discriminated and segregated from society in contemporary Britain. 2. Explain the concept of 'social role valorization' and describe how you would ensure Mabel becomes a valued member of the community. Banks, S (2001) in the book, ‘Ethics and Values in Social Work’ sheds light on the contribution of social workers in fulfilling the concept of ‘social role valorization’. Broadly speaking, people with learning difficulties are looked down upon and discriminated by society for the mere reason that they are much less productive and very little use to the community and society at large. 'Social role valorization' (SRV) is defined as  "The application of what science can tell us about the enablement, establishment, enhancement, maintenance, and/or defense of valued social roles for people" (Wolfensberger, 1995a). The primary goal of SRV is lending support to people in society so as to enable them to enjoy all the good things that society has got to offer. Some of these good things are love and friendship, respect and dignity, acceptance and belonging, good education and status in the society. In the case of people with learning disabilities, it becomes impossible for them to find a valued place in society since th ey are not in a position to contribute to their community and society and automatically become devalued members of society. Hence being devalued members of society, they are not in a position to enjoy the good things in life. On the other hand, such members are rejected by their community and society, and thereby receive a lot of negative responses and in most cases become objects of abuse and violence. SRV is a response to such groups of devalued members and lends great support in helping them to become

Some aspect of distribution theory Article Example | Topics and Well Written Essays - 250 words

Some aspect of distribution theory - Article Example One of the books that I bought is titled, â€Å"The Accident†. This book is available in the Amazon UK and can also be accessed in other networks such as eBay and other online marketing Companies. The use of online modes of distributing goods and services has not only been used in books, but also in other products for instance: Currently one can order for a movie online; one of the main sources on distributing such products are online marketing channels such as Amazon uk, the eBay and others that are used in various parts of the world such as the OLX, which was recently introduced. My encounter with purchasing a book from the Amazon, was greatly successful, the process of purchase is quite simple as it involves filing in personal details such as the address i.e. place of delivery and the payment details. The delivery is made by the company to the client, making the process efficient in relation to time

Perforation of Composite Sandwich Panels

Perforation of Composite Sandwich Panels CHAPTER 1 INTRODUCTION 1.1 Introduction The use of sandwich structures has been increasing in recent years because of their lightweight and high stiffness. Commonly, the naval industry and transportation uses the E-glass fibers while the aerospace industry uses composite structures such as carbon fiber. The use of sandwich panels with composite facesheet in the naval industry is particularly appealing because they have better corrosion and environmental resistance and reduced magnetic signatures when compared to double-hull construction steel ships. On the other hand, composite sandwich panels are easily susceptible to damage by a strange object impact. The damage may be visible, penetration or perforation, or invisible, internal delamination and debonding. Both types of damages will result in stiffness and strength reduction. It is then important to study the impact behavior of composite sandwich panels. Failure in composite structures can be caused by low, high and extremely high or localized impact. An impact caused by a foreign body initiates two waves from impact point in a panel: a through-thickness wave and a transverse shear wave. Whether or not these waves play an important role in the impact response of the panel depends on the actual contact duration between the projectile and panel and the time it takes the transverse shear wave to reach the panel boundary. Figures 1.1 (a)-(c) show three-impact scenarios: low-velocity, high-velocity and ballistic impact. In low-velocity impact, the contact force duration is long compared to the time it takes the transverse shear wave travel to reach the plate boundary. Many waves reflect back and forth across the side dimension of the panel. In high-velocity impact, the contact force duration is much shorter than the transverse shear wave travel time through the panel. Usually high-velocity impact is the same with perforation and localized damage of the panel. Ballistic impact deals only with through-thickness wave propagation. During ballistic impact, there is complete perforation of the panel with little or no panel deformation. The contact force duration is approximately the wave travel time through the panel thickness. Ballistic impact usually involves the study of penetration mechanics. Low-velocity High-velocity Ballistic Impact The projectile to panel mass ratio will control whether wave propagation effect dominates the panel impact response and then suggested that a mass ratio be use as a parameter to determine impact response. It was shown that small mass impacts produce more damage than high-mass impacts having same kinetic energy. While small-mass impacts were defined by wave-controlled response, large mass impacts were defined by boundary-controlled response. Common examples of low-velocity impact are of bird strikes, collision with floating object, and dropped tools, may cause damage. Underwater blast or debris from a faraway explosion and air was considered as a high-velocity impact situation. Examples of ballistic impact would be a bullet or fragments from a nearby explosion hitting the panel. Another important factor governing the impact on composite structures is the ballistic limit. The ballistic limit is defined as the highest velocity of the projectile to cause perforation. When the residual velocity (exit) of the projectile is zero, then the initial velocity of the projectile that causes perforation is the ballistic limit of the sandwich panel. The ballistic limit may be calculate analytically or determined experimentally. In the experimental method, sandwich panels are shoot with projectiles over narrow range of velocities to either just cause penetration or to just perforate the panel. There exists a striking velocity at which 50% of the panels are completely perforate above this value and remaining 50% are partly penetrate below this value. This striking velocity is expresse as V50, which is the ballistic limit of the panel. In the analytical approach, the ballistic limit is determined by the conservation of energy principle. The approach is complex because it inc ludes a variety of factors like core thickness, facesheet thickness, shape of the projectile, core crushing stress, and so on. 1.2 Problem Statement This topic was an expansion of the Wan Awis research. He has done only an experimental work. For impact application, we need to predict skin and core material thickness. Since impact phenomena depend on numerous parameters such as material properties or projectile geometry, a numerical model, validated experimentally, is necessary to allow the study of the influence of several parameters without making costly experimental tests. This will definitely enhance the development of our military technology and achievements in the future because of the ability of this software to cut production cost and time consuming of the experimental work. The numerical figures have been compared to modal test results aiming mainly to validate the studies. Simulation based on finite element analysis (FEA) must not exceed  ± 15% error or this simulation could be claimed not acceptable. 1.3 Objective To simulate the damage of composite sandwich structures subjected to high-velocity impact using finite element analysis. To determine the energy absorption capability of the components on the behavior of the sandwich panel under impact load using ANSYS AUTODYN 13.0 To validate a numerical model with actual experiment. 1.4 Scope of Works To characterize a mechanical behavior of carbon fiber panel by using tensile and determine the fiber volume force and density. Design and validate the numerical model. Conduct a ballistic impact test simulation. Using the experiments data to calculate the energy absorption on the impact. CHAPTER 2 LITERATURE REVIEW 2.1 Introduction A great deal of research has been conducted in the area of impact of composite structures. In this chapter, previous work done on the impact response of laminated composite plates and composite sandwich panels will be reviewed. 2.2 Impact of Composite Laminates A detail study of impact of composite laminates in the three impact regimes ballistic impact, low-velocity and high-velocity is presented in this section. 2.2.1 Low-velocity Impact Abrate, 1998 give a specific review on different analytical models of impact on composite laminates. He classified impact models into four groups: impact on infinite plate model, energy balance models, spring-mass models, and complete models. In the energy balance model, the initial kinetic energy of the projectile is used to calculate the deformation of the composite laminate. The velocity of the projectile reaches zero at the maximum deflection of the composite laminate. At this point, all of the kinetic energy of the projectile is converted to strain energy needed to deform the composite laminate. Energy balance model assumes that the structure behaves in quasi-static manner. The time history of force and deflection are obtained using the spring-mass model representing the composite laminate. The model shown in Figure 2.1 consists of nonlinear contact stiffness (K), one spring representing the linear stiffness of the structure (Kbs), another spring for the nonlinear membrane stiff ness (Km), effective mass of the structure (M2) as well as the mass of the projectile (M1). Equations of motion are written from a free body diagram. The infinite plate model is used when the deformation wavefront has not reached the boundary but if the wave reaches the plate boundary then this model is not an appropriate one to use. In the complete model, the dynamics of the structure and projectile are taken into explanation. Appropriate plate theory has to be selected and used. In many cases the classical plate theory can be used but when transverse shear deformations become significant, higher-order theories must be used. One of the earliest studies on the impact of composite laminates was by Goldsmith et al, 1995, who conducted high-velocity and quasi-static impact tests on carbon-fiber laminates by using a cylindro-conical projectile. Three different specimen of varying thickness were considered. Energy balance principle was used to predict the dynamic penetration energy, static penetration energy, and also the ballistic limit of the composite laminate. The fiber failure accounted for most of the energy absorbed. The predicted theoretical energy was in good agreement with measured energy for thin laminates but not for the thick laminates. This was approved to the fact that transverse shear deformation played an important responsibility in thick laminates subjected to low-velocity impact. The effect of transverse shear deformation was not dominant due to its quick occurrence in the high-velocity impact of laminates. Therefore, the predicted energy in the dynamic case was always close to but less than the measured energy for the thin and thick laminates. The predicted ballistic limit was less than measured values due to the nonlinear factors. Cantwell, 2007 studied the influence of target geometry in the low-velocity impact of composite laminate. The tests were performed on GFRP plates with hemispherical indenter on either circular or square supports. He used energy-balance model to predict the plate deflection and the delamination area of the laminated structure. His study stated that there is little or no influence of target geometry on the failure modes. It also suggested that delamination was dependent on interlaminar shear stress and increasing the plate diameter required more energy for damage initiation. Hou et al., 2000 predicted impact damage in composite laminates using LSDYNA 3D. The numerical results were compared to experimental results on low-velocity impact on composite laminate with an initial velocity of 7.08 m/s The Chang-Chang failure criteria was modified taking the shear stress into consideration and the model was implemented in DYNA 3D. 2.2.2 High-velocity Impact In 1988, Cantwell performed high-velocity impact tests of CFRP laminates with 6 mm diameter, 1g steel ball as the projectile. The influence of fiber stacking sequence and target geometry was study. The experiments reveal that varying the target geometry had no significance on initial damage caused. While the damage initiated in the distal facesheet in thin laminates, however, in thick laminates it initiated from incident facesheet. Zhao et al., 2007 investigated the failure modes in composite laminates subjected to high-velocity impact. Three different laminates were subject to impact by hemispherical projectile in the range of 10-300 m/s. An energy balance was considered and equations for residual velocity for the laminates were given in terms of the mass of the projectile and striking velocity. The thickness and stacking sequence were finding to play an important role in the energy absorption. Cheng et al., 2007 developed an analytical model based on the spring-mass model for high-velocity impact of a blunt ended and a sharp-ended projectile on thick composite laminates. They considered the effect of moving boundary due to the propagation of shear wave. The analysis was modeled using series of quasi-static events. At the end of each quasi-static step, the failed layers were remove based on punch shear damage and fiber damage criteria, and the wave front was moved outwards. While the first spring stiffness constant was measure based on the penetration depth of the projectile, the second spring stiffness constant was measured based on the bottom node of the plate. 2.2.3 Ballistic Impact Silva et al., 2005 performed numerical simulations of ballistic impact on thin Kevlar 29 composite laminates using a fragment-simulating projectile. The laminate material model was simulating using AUTODYN and the projectile was modeled using Johnson-Cook strength model. Finite element mesh for both laminate and projectile was generating using True Grid. Accurate predictions of ballistic limit (V50) and the failure modes were made. Ballistic limit is the minimum velocity of impact at which a given projectile just perforates a given target. On occasion, the term is also used to identify the maximum impact velocity at which the projectile can penetrate into the target with perforation. It is often defined statistically as the impact velocity for which the projectile has a 50% probability of perforating the target; it is then denoted by V50. Guild et al., 2007 conducted numerical simulations of ballistic impact on composite laminates and compared them with experimental results. The laminates were made of E-glass/vinyl ester resin with varying thickness and ball bearings of varying mass were use as projectiles. The damage modes included fiber failure, matrix failure, penetration, and delamination. Hashin failure criteria was use to determine the damage mode. Delamination was modeled using an interface between the two plies. As the force increased between two nodes above the specified value, the nodes were untied and the delamination increased. The ballistic limit from experiments was in good agreement with numerical results Naik et al., 2008 studied the ballistic impact behavior of thick composites. E-glass/epoxy laminates of varying thickness were subject to high-velocity impact. The effects of projectile diameter, projectile mass and laminate thickness on the ballistic limit were studied. Wave theory and an energy balance were use to predict the ballistic limit of the laminate. The contact duration of the projectile with the laminate was maximum when the initial velocity was equal to ballistic limit and decreased when the initial velocity increased beyond the ballistic limit. Deka et al., 2008 conducted ballisitic impact on E-glass/polypropylene composite laminates with cylinder-shaped projectiles. The experimental results were validating with numerical analysis using LS-DYNA. Although the laminate was modeling in Hypermesh, LS-DYNA was used to analyze failure mechanisms. The analytical model was base on energy conservation and failure in the numerical analysis was predicted based on Hashins failure criteria. 2.3 Impact of Composite Sandwich Panels In this section, a detail study of impact of composite sandwich panels in the three impact regimes low-velocity, high-velocity and ballistic impact is presented. 2.3.1 Low-velocity Impact Mines et al., 1998 investigated quasi-static loading and low-velocity impact behavior on two different composite sandwich panels. While the first panel was made up of E-glass/vinyl ester skin and Coremat ® core, the second panel was made of Eglass/epoxy skin and aluminium honeycomb core. The first panel with Coremat ® core had failed in the sequence of core shear, debonding, and distal facesheet damage and incident facesheet failure. The second panel failed by core shear, debonding, incident facesheet failure and then distal facesheet failure later. In the low-velocity impact tests, the failure pattern remained the same in both the panels as of the quasi-static tests. The core properties and impact velocity govern the energy absorption capability of the sandwich panel. Wen et al., 1998 investigated the penetration and perforation of composite laminates and sandwich panels under quasi-static, drop-weight and ballistic impact tests by flat-faced, hemispherical-ended and conical-nosed indenters/projectiles. They categorized the impact on laminates and sandwich panels into low-velocity impact and wave-dominated (high-velocity/ballistic impact) response. It was also stated in the research that sandwich panels subjected to low-velocity impact have similar load-displacement characteristics as of quasi-static loading case. The perforation energy required by flat faced projectile was more than hemispherical-ended and conical shaped projectiles in high-velocity impact. Schubel et al., 2005 investigated quasi-static and low-velocity impact behavior of sandwich panels with woven carbon/epoxy facesheets and PVC foam. The low-velocity impact model behaved similar to quasi-static loading case when loads and strain levels were same. The static indentation response was compared to the numerical results obtained using ABAQUS and were in good agreement. A membrane solution, assuming membrane in the core affected region and plate on elastic foundation in the rest of sandwich panel was in poor agreement with the numerical results. Hoo Fatt et al., 2001, developed static and dynamic models of sandwich panels subjected to low-velocity impact. They investigated the behavior of sandwich panels having carbon/epoxy skins and a Nomex honeycomb core with a hemispherical indenter under various support conditions such as simply supported, fully clamped, and rigidly supported. Spring-mass models were considered to determine the load-displacement curve. They also investigated the damage initiation of sandwich panels under low-velocity impact loading. The initial mode of damage depended upon the panel support conditions, projectile nose shape, geometry of the specimens, and material properties of the facesheet and core. Various failure patterns were studied and solutions based on them were derived separately. The analytical solution for the ballistic limit was also found and results for thick laminates were in better agreement than thin laminates. Suvorov et al., 2005 performed numerical analysis on sandwich panels with foam core and studied the effect of interlayer in between the top facesheet and foam core. The foam core was modeled as crushable foam in ABAQUS. While the polyurethane (PUR) interlayer reduced the deformations in both the core and the composite facesheets, the elastomeric foam (EF) interlayer offered a better protection for the foam core alone. Besant et al., 2001 performed numerical analysis on sandwich panels with aluminium honeycomb core. The metal honeycomb core was modeled as elastic perfectly plastic material. A quadratic yield criterion was proposed for the core material, which included both normal and transverse shear stresses. The importance of core plasticity in finite element analysis was explained. 2.3.2 High-velocity Impact A great deal of work has been done in the area of low-velocity impact of laminates and sandwich panels and high-velocity impact of laminates but limited work has been presented in the domain of high-velocity and ballistic impact of sandwich panels. The following describes some recent studies on the high-velocity impact of composite sandwich panels Velmurugan et al., 2006 studied the projectile impact on composite sandwich panels in the range of 30-100 m/s. The sandwich models in this study were not the typical sandwich panels in the conventional sense. They had a core height comparable to the facesheet thickness and acted as a bonding agent between the facesheets. Energy-balance model was used to determine the ballistic limit of three different sandwich panels. They assumed the sandwich panel as a single plate since the foam layer was thin and comparable to facesheet thickness. Also uniform failure mechanism along the through thickness direction was assumed in their model. Skvortsov et al., 2003 developed an analytical model using energy-balance principle to determine the ballistic limit of composite sandwich panels subjected to high velocity impact. Two different sandwich panels were subjected to high velocity impact using three different projectiles. These tests were conducted on simply supported and rigidly supported boundary conditions, and the initial velocity was varied in the range of 70-95 m/s. The predicted panel energy was close to the experimental values and the error was due to the strain-rate effects, plastic behavior, and hardening phenomena, which are not consider in the analysis. 2.3.3 Ballistic Impact Kepler et al., 2007 conducted ballistic impact on sandwich panels consisting of GFRP plates and Divinycell H80 core, with three different projectiles. Lumped spring mass model was use to calculate force histories and panel response. Concentric rings connected by shear springs represented the sandwich panel. In this model, core shear deformation was assumed as the single significant contributor to the sandwich panel stiffness. The facesheet orthotropic was neglected in the panel response. Four different force histories: constant force, triangular force, sine series, and combination of sine and triangular force were used to calculate the energy loss in the panel. Of these, triangular and combined force gave results in better agreement with experimental results. 2.4 Aluminium Honeycomb For design and construction of lightweight transportation systems such as satellites, aircraft, high-speed trains and fast ferries, structural weight saving is one of the major considerations. To meet this requirement, sandwich construction is frequently use instead of increasing material thickness. This type of construction consists of thin two facing layers separated by a core material. Potential materials for sandwich facings are aluminium alloys, high tensile steels, titanium, and composites depending on the specific mission requirement. Several types of core shapes and core material are been applied to the construction of sandwich structures. Among them, the honeycomb core that consists of very thin foils in the form of hexagonal cells perpendicular to the facings is the most popular. A sandwich construction provides excellent structural efficiency, i.e., with high ratio of strength to weight. Other advantages offered by sandwich construction are elimination of welding, superior insulating qualities and design versatility. Even if the concept of sandwich construction is not very new, it has primarily been adopt for non-strength part of structures in the last decade. This is because there are a variety of problem areas to be overcome when the sandwich construction is applied to design of dynamically loaded structures. Other investigators have previously carried out noteworthy theoretical and experimental studies on linear elastic and nonlinear behavior of aluminium sandwich panels. Kelsey et al., 1985 derived simple theoretical expressions of the shear modulus of honeycomb sandwich cores. Witherell, 1977 performed an extensive theoretical study for structural design of an air cushion vehicle hull structure using aluminium honeycomb sandwich panels. Okuto et al., 1991 showed the validity of the so-called equivalent plate thickness method in which a honeycomb sandwich panel subjected to inplane loads is approximately replaced by a single skin panel with equivalent plate thickness. Kobayashi et al., 1994, studied Elasto plastic bending behavior of sandwich panels. An experimental study was undertaken by Yeh et al., 1991 to investigate the buckling strength characteristics of aluminium honeycomb sandwich panels in axial compression. Kunimo et al., 1989 both, have studied the characteristics of the energy absorption capacity of bare honeycomb cores under lateral crushing loads theoretically and experimentally. 2.5 Ballistic Limit The ballistic limit may also be defined as the maximum velocity at which a particular projectile is expected to consistently fail to penetrate armor of given thickness and physical properties at a specified angle of obliquity. Because of the expense of firing tests and the impossibility of controlling striking velocity precisely, plus the existence of a zone of mixed results in which a projectile may completely penetrate or only partially penetrate under apparently identical conditions, statistical approaches are necessary, based upon limited firings. Certain approaches lead to approximation of the V50 Point, that is, the velocity at which complete penetration and incomplete penetration are equally likely to occur. Other methods attempt to approximate the V0 Point, that is, the maximum velocity at which no complete penetration will occur 2.6 Energy Absorption Mechanism of Composite Materials The research was done by Naik and Shrirao at 2004. Impact loads can be categorized into three categories which is low-velocity impact, high-velocity impact and hyper-velocity impact. This classification is made because of change in projectiles velocity will result in different mechanisms in terms of energy transfer between projectile and target, energy dissipation and damage propagation mechanism. Basically, ballistic impact is considered as low-mass high velocity impact. In this impact event, a low-mass projectile is launched by source into target at high velocity. It is unlike low-velocity impact that involved high-mass impactor impacting a target at low velocity. In view of the fact that ballistic impact is high velocity event, the effect is localized and near to impact location. According to Naik et al. (2006), seven possible energy absorbing mechanisms occur at the target during ballistic impact. Those mechanisms are cone formation at the back face of the target, deformation of secondary yarns, tension in primary yarns/fibres, delamination, matrix cracking, shear plugging and friction between the projectile and the target. Then, the researchers formulated all these energies into equation whereby the total energy absorbed by the target is summation of kinetic energy of moving cone EKE, shear plugging ESP, deformation of secondary yarns ED, tensile failure of primary yarns ETF, delamination EDL, matrix cracking EMC and friction energy EF. ETOTALi = EKEi + ESPi + EDi + ETFi + EDLi + EMCi + EFi Mines et al. (1999) identified three modes of energy absorption when analysed the ballistic perforation of composites with different shape of projectile. These energy absorptions are local perforation, delamination and friction between the missile and the target. However, the contribution of friction between the missile and the target in energy absorption is low compared to the other two. In terms of local perforation, three through-thickness regimes can be identified, namely: I shear failure, II tensile failure and III tensile failure and delamination. Out of these three regimes, the through-thickness perforation failure is dominated by shear failure. Similar observation has been made by other researcher for thick graphite epoxy laminates whereby the perforation failure is dominated by shear failure. The third main energy absorption mechanism is delamination. Delamination can propagate under Mode I (tensile) and Mode II (shear) loading and each mode can dominate each other depend ing on structural configuration of the composite as well as material properties. Therefore, it can be predicted that the total perforation energy is a summation of energy absorption due to local perforation, delamination and friction between the missile and the target. Epred = Ef + Esh + Edl where Ef = friction between the missile and the target; Esh = local perforation; Edl = delamination Apart from that, Morye et al. (2000) has studied energy absorption mechanism in thermoplastic fibre reinforced composites through experimental and analytical prediction. They considered three mechanisms that involved in absorbing energy by composite materials upon ballistic impact. The three energy absorption mechanisms are tensile failure of primary yarns, elastic deformation of secondary yarns and the third mechanism is kinetic energy of cone formed at back face of composite materials. They concluded that kinetic energy of the moving cone had a dominant effect as energy absorption mechanism for composite materials. However, they neglected a delamination as one of the factor contributed to the failure of composite materials during ballistic impact. 2.7 Kinetic Energy Equation Kinetic energy (KE) attack is a penetration of the residual energy of a projectile. A projectile can give a certain amount of energy to attack and damage a vehicle if the projectile sufficient residual energy when it arrive at the target. This residual is very important to overmatch the capability and strength of the target material to resist penetration, and then it will penetrate. Kinetic energy shot can be presented with the simple law of physic. K.E =  ½ Mprojectile Vprojectile2 Increasing the mass (Mprojectile) of the shot increases its energy, but the real payoff comes from increasing its velocity (Vprojectile). If the diameter of the shot fills the whole gun barrel, the projectile becomes heavier and difficult to accelerate to required velocity with the length of the barrel. Additionally, a large diameter solid shot will provide more energy to penetrate the armour plate compared to a projectile which has the same mass but a smaller diameter. Consequently, the larger shot is not only less effective at the target but it is difficult to give it the necessary velocity. According to Chang et al., 1990, depth of penetration at the target will depend not only on residual energy, but also on shape and size of the projectile. The curve shape at the projectile head is more important, as it must not only able to pierce the armour but the shoulders of the shot must also support the remainder so that it does not break up on its way through the armour. If for given mass the diameter of the shot is reduced and is length increased, then for the same residual energy the shot will penetrate further, as it is working on a smaller cross section area of armour. The ratio of length-to-diameter is called slenderness ratio. Any projectile with ratio in excess of 7:1 cannot be spin stabilized it is not until they reach a ratio approximately 20:1 that they can call long rod. So, based on those discussions above, we can conclude that energy absorption can be performed by this relation Eabsor = Ein Eout = [ ½ Mprojectile Vin2] [ ½ Mprojectile Vout2] =  ½ Mprojectile (Vin2 Vout2) So, Eabsorbed =  ½ Mprojectile (Vin2 Vout2) 2.8 Tsai-Hill Failure Criterion Hill, 1950 proposed a yield criterion for orthotropic materials: G+HÏÆ'12+F+HÏÆ'22+F+GÏÆ'32-2HÏÆ'1ÏÆ'2-2GÏÆ'1ÏÆ'3-2FÏÆ'2ÏÆ'3+2LÏ„232+2MÏ„132+2NÏ„122=1 This orthotropic yield criterion will be used as an orthotropic strength or failure criterion in the spirit of both criteria being limits of linear elastic behavior. Thus, Hills yield stresses F, G, H, L, M and N will be regarded as failure strengths. Hills criterion is an extension of von Mises yield criterion. The von Mises criterion, in turn, can be related to the amount of energy that is used to distort the isotropic body rather than to change its volume. However, distortion cannot be separated from dilatation in orthotropic materials, so Equation 2.8 is not related to distortional energy. Unfortunately, some authors still mistakenly call the criterion of Tsai-Hill a distortional energy failure criterion. The failure strength parameters F, G, H, L, M and N were related to the usual failure strength X, Y, and S for a lamina by Tsai. If only Ï„12 acts on the body, then, because its maximum value is S, 2N=1S2 Similarly, if only ÏÆ'1 acts on the body, then G+H=1X2 And if only ÏÆ'2 acts, then F+H=1Y2 If the strength in the 3-direction is denoted by Z and only ÏÆ'3 acts, then F+G=1Z2 Then, upon combination of Equations (2.10), (2.11) and (2.12), the following relations between F, G, H and X, Y, Z result: 2F=1Y2+1Z2-1X2 2G=1X2+1Z2-1Y2 2H=1X2+1Y2-1Z2 For plane stress in the 1-2 plane of a unidirectional lamina with fibers in the 1-direction, ÏÆ'3 = Ï„13 = Ï„23 = 0. However, from the cross sectional of such a lamina in Figure 2.3, Y = Z from the obvious geometrical symmetry of the material construction. Thus, Equation (2.8) leads to ÏÆ'12X2-ÏÆ'1ÏÆ'2X2+ÏÆ'22Y2+Ï„122S2=1 as the governing

Baldwins Notes to a Native Son Essay -- James Baldwin

â€Å"If the relationship of father to son could really be reduced to biology, the whole earth would blaze with the glory of fathers and sons.† This quotation by James Arthur Baldwin helps to bring about one of the main points of his essay, â€Å"Notes of a Native Son.† Baldwin’s composition was published in 1955, and based mostly around the World War II era. This essay was written about a decade after his father’s death, and it reflected back on his relationship with his father. At points in the essay, Baldwin expressed hatred, love, contempt, and pride for his father, and Baldwin broke down this truly complex relationship in his analysis. In order to do this, he wrote the essay as if he were in the past, still with his father, but reflecting on the events of the era, both private and public, from his point of view. He partially accomplished this since he experienced events of the era first hand, showing that only an African American cou ld have written the essay as he did. James Baldwin throughout the essay hovered from his own personal life to the world around him and his father. Baldwin weaves between narration and analysis in order to show that his own experiences dealing with the public world and his private world were similar to many other Americans at that time. Evidence of Baldwin’s ability to connect public events to his personal life appeared right away in the very first paragraph of the essay. Baldwin changed from story of his father’s death, a private event, to the Detroit and Harlem riots of the civil rights movement, a public event. He linked the two together through the death of his father and, â€Å"One of the bloodiest race riots of the century† (63). Baldwin immediately started to analy... ... what occurred privately and in the rest of the United States. Baldwin put his own personal thoughts and reflections into what happened in his life and the lives of everyone else like him. Baldwin himself, being African American, was another one of the reasons he was able to pull off these transitions. He related his own personal stories of what took place in his life during the troubled times of the civil rights movement to the rest of the general public. The stories Baldwin had of his father correlated to the events African Americans faced in the same time period. All these things combined allowed Baldwin to transition between narrative and analysis keeping the reader on edge and attentive. Works Cited Baldwin, James. â€Å"Notes of a Native Son.† 1955. James Baldwin: Collected Essays. Ed. Toni Morrison. New York: Library of America, 1998. 63-84.

Jose Rizal Essay

I. Introduction Jose rizal and andress bonifacio, ever heard of those name? what about their contribution and sacrifices for you as a Filipino? have you heard/know something about it? two people with the same desire and love for the country but has different beliefs and ways on acquiring their wants. Two people who came from the past and lived a greatest mark on the history of our nation, a men who awaken the desire of every indios in acquiring the freedom that was taken away from them for almost 300 years. Jose rizal was known from being the national hero of the Philippines. Who wouldn’t know about him? He was in every history book of phil. Same as bonifacio. They both sacrifice their lives to prove how much they love their country and for their desire to see the Philippines as a country having its own freedom and sovereignity. This research paper will tackle the nationalistic movement of jose rizal and andress abonifacio. II. Jose Rizal and his Nationalistic Movement Jose Rizal felt so guilty in Spaniards of being harsh and abusing Filipino people. Rizal form a organization called propaganda movement. The Propaganda Movement was a literary and cultural organization formed in 1872 by Jose Rizal. The aim of the propaganda movement was a peaceful assimilation, referring to the transition of the Philippines from being a colony to a province of Spain. These reforms were as follows: equality of the Filipinos and Spaniards before the laws; restoration of the Philippine representation in the Spanish Cortes; secularization of the Philippine parishes and the  expulsion of the friars, and human rights for Filipinos, such as freedom of speech. Freedom of the press and freedom to meet and petition for redress of grievances. Those who join this peaceful campaign were the Filipino exiles of 1872, the patriots who left the islands to escape persecution, and those who had been to Spain for their studies. Another Movent of Jose Rizal is The La Liga Filipina. social background is illumined and concretely defined by individual acts of intervention, such as Rizal’s novels, without which society and the physical world remain indifferent. We need this dialectical approach to comprehend in a more all-encompassing way Rizal’s vexed and vexing situation, together with his painstakingly calculated responses—all cunning ruses of Reason in history (for Hegel). Such ruses actually register the contradictions of social forces in real life, reflected in the crises of lives in each generation. The substantial biographies of Rizal–from Austin Craig to Rafael Palma, Leon Maria Guerrero to Austin Coates–all attempted to triangulate the ideas of the hero with his varying positions in his family, in the circle of his friends and colleagues in Europe, and in relation to the colonial Establishment. Their main concern is to find out the origin of the hero’s thoughts and their impact on the local environment. But the twin errors of contemplative objectivism and individualist bias persisted in vitiating their accounts. They ignored the historical-materialist axiom that the changing of circumstances and of personal sensibility/minds, as Marx advised, â€Å"can be conceived and rationally understood only as revolutionary practice†Ã¢â‚¬â€that is, sensuous collective praxis in material life. In Palma’s biography, for example, the novelty of Rizal’s project of the Liga Filipina became simply â€Å"a means to defray the expenses of the colonization of Borneo† (1949, 202; see Zaide and Zaide 1984). In reality, the Liga is the chief emblematic index of that transformative praxis fusing personal experience and objective circumstances. It is the crucible marking the failure of La Solidaridad reformism and the transition to the stage of popular mobilization mediated by the rising organic intellectuals of the dispossessed, in particular Andres Bonifacio, Jacinto, and others. Rizal’s radicalizing agenda was already distilled in his bold testimony of communicative action, the eloquent â€Å"Letter to the Women of Malolos†(more later), and articulated in the two letters dated June 20, 1892, letters whose resonance andvalue can  perhaps be compared only to St. Paul’s epistles to the early converts of the faith. By all accounts, the formation of the Liga is the key event marking Rizal’s leap from intellectual gradualism to collective separatism. Before his exile to Dapitan in 1892, Rizal met with members of the Masonic Balagtas Lodge in the home of Doroteo Onjungco, including Ambrosio Salvador, Timoteo Paez, Pedro Serrano, Domingo Franco, and, last but not least, Andres Bonifacio, who was then not distinguishable from the crowd of about thirty individuals. After Governor Despujol decreed Rizal’s banishment, the Liga members met secretly in the Azcarraga apartment of Deodato Arellano, among them Andres Bonifacio and Gregorio Del Pilar, who later died fighting American troops pursuing the fleeing Aguinaldo headed for Palanan (Palma 1949, 225). That historic gathering of seven persons signaled the launching of the Katipunan, The organization of â€Å"sons of the people† committed to overthrowing Spanish colonial tyranny. References: http://reference.allrefer.com/country-guide-study/philippines/philippines20.html http://en.wikipedia.org/wiki/Propaganda_Movement http://en.wikipedia.org/wiki/Filipino_nationalism

Argumentative Reflection War Essay

Nobody likes war; it is so costly in so many ways. Lives are lost, property is destroyed, people are injured and some are disabled mentally and physically. Because of this many people think war must be avoided at all costs. All these facts regarding the high cost of war on a country are true. On the other hand there are situations in which a nation has an obligation to go to war. Their were many times in the United States history when the decision to enter a war was in question. World War II was a time when people were arguing about whether or not the United States should enter a war against Germany, Japan and their allies. When this war started WWI was still fresh in people’s memories. The citizens knew how bad war could be. Many people felt that these new problems were not the United States problems and war should be avoided. Author Jon Bridgman tells us in an article in the Seattle Post- Intelligencer â€Å"The nation was deeply and bitterly divided on the question of our participation in the war. American isolationists felt that the war in Europe and Asia was not our problem and that we should stay out of it†. Of course other people knew that war was going to come, because Germany and Japan were proving they wanted to take over the world. The argument was settled by Japan. There sneak attack on Pearl Harbor solved the argument. They forced us into the war. The attack they made in Pearl Harbor was a direct attack on the United States military and a direct attack on United States land. Now US citizens knew it was all out war for the countries survival. On September 11, 2001 the US was again attacked. This time it wasn’t by another country but by terrorists. It was similar to the Pearl Harbor attack because Americans were surprised and thousands of people lost their lives. The big difference was that the attack was not done by a country but by terrorists from many different countries. The citizens of the United States pretty much agreed that this was an evil act and that the terrorists needed to be stopped so that they could not attack again. The problem was that it was not a country that attacked but a terrorist group hiding and spread out across several countries. Who could the United States blame and hold responsible for the attacks? President George Bush immediately blamed Afghanistan and later Iraq for letting terrorists use their countries to train and operate. He felt these countries should be attacked so terrorists could be stopped. The President sent our troops to Afghanistan and the troops were successful in that area and then President Bush decided the US needed to invade Iraq. This is when the argument about going to war in another country was the United States concern. A lot of people had heard that, Saddam Hussein, the leader of Iraq was a supporter of terrorists and also a threat to the world. The argument about attacking Iraq was big. If you look b ack to 2003 when people were arguing this you can see that their was enough people who wanted to go to war. Nicholas Lemann wrote in an article in the New Yorker magazine that â€Å"Everyone agrees that Saddam Hussein is truly evil, everyone agrees he has weapons of mass destruction†. On the other side of the argument many countries and people disagreed with attacking Iraq. Many inspections done by the United Nations could not find weapons of mass destruction. President Bush eventually convinced the United States Congress that Iraq was dangerous and the US army attacked Iraq. It turned out after a tough fight, the United States military could not find any weapons of mass destruction. A report in the Washington Post said â€Å"The new report from the Iraq Survey Group has confirmed beyond any reasonable doubt what most people have assumed for the past year: At the time of the 2003 U.S. invasion, Iraq did not possess weapons of mass destruction, and most of its programs to produce them were dormant.† The United States was wrong about the weapons. Even though the pro- war people were wrong about the weapons of mass destruction they felt that they were stopping a horrible dictator who could have been a big threat in the future. At least the army fought terrorists because as the war dragged on the United States did eventually find itself fighting terrorists because many terrorists came to Iraq to face the United States army. Lionel Beehner reported in the Backgrounder magazine that â€Å"Large-scale suicide attacks in Iraq are up in recent months, demonstrating that al-Qaeda in Iraq and its homegrown affiliates remain a potent force.† In both of these cases the United States went to war to provide safety for United States citizens. In both these cases the United States was attacked. In both these case people debated and argued about going to war .Yes many people were killed and injured but these examples show that there is definitely situations when a country is obligated to go to war. Works Cited John Bridgman â€Å"Lessons learned from two days of infamy† Seattle Post -Intelligencer Sunday December 2, 2001 Nicholas Lemann â€Å" How It Came To War† The New Yorker March 31, 2003 Editorial â€Å"Weapons That Weren’t There† The Washington Post October 7,2004 Lionel Beehner â€Å"Al-Qaeda in Iraq: Resurging or Splintering? Backgrounder