Finite Pure Plane Strain Bending of Inhomogeneous Anisotropic Sheets

The present paper concerns the general solution for finite plane strain pure bending of incompressible, orthotropic sheets. In contrast to available solutions, the new solution is valid for inhomogeneous distributions of plastic properties. The solution is semi-analytic. A numerical treatment is only necessary for solving transcendent equations and evaluating ordinary integrals. The solution’s starting point is a transformation between Eulerian and Lagrangian coordinates that is valid for a wide class of constitutive equations. The symmetric distribution relative to the center line of the sheet is separately treated where it is advantageous. It is shown that this type of symmetry simplifies the solution. Hill’s quadratic yield criterion is adopted. Both elastic/plastic and rigid/plastic solutions are derived. Elastic unloading is also considered, and it is shown that reverse plastic yielding occurs at a relatively large inside radius. An illustrative example uses real experimental data. The distribution of plastic properties is symmetric in this example. It is shown that the difference between the elastic/plastic and rigid/plastic solutions is negligible, except at the very beginning of the process. However, the rigid/plastic solution is much simpler and, therefore, can be recommended for practical use at large strains, including calculating the residual stresses.

Design and development of soft robotic hand for vertical farming in spacecraft

<p>For colonization in deep space we need to explore the feasibility of a bioregenerative system in microgravity or artificial gravity environments. The process has various complexities form ranging to biological obstacles to engineering limitations of the spacecraft. Concentration of microbes in the confinements of a spacecraft can be fatal for the crew. In this paper, a solution to the elevated microbial levels by farming using robots is discussed. The soft robotic arm is made up of Asymmetric Flexible Pneumatic Actuator (AFPA). The AFPA under internal pressure will curve in the direction of the side having greater thickness as the expansion of the thinner side (outside radius) will be more than thicker side (inside radius) due to differential expansion and moment induced due to eccentricity. Simulation results demonstrate that bending based on AFPA can meet the designed requirement of application. The AFPA is used for five fingers of the robotic hand. The safe, soft touch and gentle motion of the bellow (AFPA) gives the feel of real human hand. The internal pressure of the AFPA is controlled using a solenoid valve which is interfaced using an Arduino microcontroller for hand like moves. The bending of the fingers and degree of freedom (DOF) of the joints of the hand is controlled using an IMU and flex sensor. Wireless connection of the hand and the control system is implemented using XBee pro 60mW with a range of 1 miles.The pneumatic soft robotic hand is made up of solenoid valve, Mini Compressor, AFPA bellow, and Servos. This soft robotic hand has many advantages such as good adaptability, simple structure, small size, high flexibility and less energy loss. As an extension Manual control of the robot using a virtual reality environment and well as some possible aspects of an automated farming systems can be considered as future additions.</p>

Titanium Hot Stretch Forming: Experimental and Modeling Residual Stress Analysis

Titanium alloys, due to their high mechanical properties coupled with light weight and high corrosion resistance, are finding a widespread use in the aeronautic industry. The use of titanium in replacing the conventional alloys, such as aluminum alloys and steel, is reduced by both the high cost of the raw material (it costs anywhere from 3 to 10 times as much as steel or aluminium) and the machining costs (at least 10 times that to machine aluminium). For such a reason new technologies have been studied and developed. In particular many researchers are searching for technologies, such as the precision hot forming, that allows to obtain components with a low buy to fly ratio. Many of the airframe component structures are designed to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot titanium forming techniques, the HSF guarantees a saving in material and machining time, which are two serious cost issues for todays aircraft manufacturers. In addition, the process allows for consistent quality in a productively efficient manner, assuring the sustainable attainment of delivery and build schedules. In order to develop and improve the HSF process a modeling of the process itself was executed in order to study the stresses and strains undergone by the material among the deformation. The FEM model was validated through the residual stresses, and in particular the residual stresses provided by the model were compared with the ones experimentally measured using the hole drilling technique. Good agreement, in terms of stress range, was recorded both for the maximum and the minimum stress.

Hot Stretch Forming of a Titanium Alloy Component for Aeronautic: Mechanical and Modeling

The development of Hot Stretch Forming (HSF) by the Cyril Bath Company was in response to airframe designers needing to use Titanium airframe components in new commercial aircraft. Many of the airframe component structures are designed to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot titanium forming techniques, the HSF guarantees a saving in material and machining time, which are two serious cost issues for today’s aircraft manufacturers. In addition, the process allows for consistent quality in a productively efficient manner, assuring the sustainable attainment of delivery and build schedules. The HSF is an innovative process on the cutting edge of the technologies, so focused research is needed in order to better understand this technology and develop new applications for this process. in this paper the HSF process is investigated: the machine and the different steps that characterized the process were described and the results of a preliminary experimental campaign was discussed focusing the attention on the metallurgical aspect. Moreover a modeling of the process was executed in order to study the stresses and strains undergone by the material among the deformation.

THE INCLUSION INSIGHT OF –CH3 AND –CH2OH MODIFIED β-CYCLODEXTRINS WITH ONE TRANS-RESVERATROL MOLECULE: A THEORETICAL STUDY

The geometries of the –CH3 and –CH2OH modified β-cyclodextrin {i.e. (β- CD(R) m ( R = –CH3, –CH2OH ; m = 0, 1, …, 7)} and the energetical behaviors of one trans-Resveratrol (TR) molecule including inside their cavities were studied by using ONIOM (B3LYP/6-31G*:PM3) method. The most outstanding geometrical characteristic of the β- CD(R) m is that their inside radius (r) are varied with different chemical modifications. The released energies for one TR molecule passing through or rotating inside the cavities of β- CD(R) m are predicted to be related with the inclusion schemes (from narrow side or wide side of the cavity), the values of the inside radius r, and the types (– CH 3 or – CH 2 OH ) and number (m) of the substituted R groups. Our calculations also suggest that the formation of H-bonds in the inclusion interaction is the main factor to stabilize the formed inclusion complexes, i.e. the TR @β- CD(R) m( R = –CH3, –CH2OH ; m = 0, 1, …, 7).

Study on Expression of SIF for Tapered Lug Subjected to Oblique Pin-Load

The finite element model of a symmetric tapered attachment lug is built by using the finite element software ANSYS, a cosine pin-bearing pressure distribution is applied on the surface of the pin-hole as a boundary condition. The stress intensity factor (SIF) expression for a single through-the-thickness crack in a symmetric attachment lug subjected to an oblique pin-load less than 45 degrees is determined by studying on the effect of the dimensionless crack length (a/R1)，the ratio of outer radius to inside radius (R2/R1), the inside radius (R1), the tapered angle (β) of lug and the load degree (α) on SIF value. The paper can be helpful in assessing and designing damage tolerant attachment lugs.

Study on Fatigue Crack Growth Model of 7075-T7410 Aluminum Alloy Straight Attachment Lug

The finite element model of a 7075-T7410 straight attachment lug is built by using the finite element software ANSYS, a cosine distribution pin-bearing pressure is applied on the surface of the pin-hole as a boundary condition. The stress intensity factor (SIF) expression for the straight attachment lug with a single through-the-thickness crack and subjected to an axial pin-load is determined by studying on the effect of the geometric parameters (the dimensionless crack length a/R1，the ratio of outer radius to inside radius R2/R1 and the inside radius R1) on SIF value. The fatigue crack growth velocity (da-dN) and the stress intensity factor’s amplitude (ΔK) is calculated by the SIFs equations to get the values of the Paris constants, offering an analytical method for establishment of the fatigue crack growth model of the typical straight lugs. The paper can be helpful in assessing and designing damage tolerant attachment lugs.

Study on Fatigue Crack Growth Model of Attachment Lug Subjected to Oblique Pin-Load

The finite element model of a straight attachment lug subjected to an oblique loading less than 45 degrees is built by using the finite element software ANSYS, a cosine pin-bearing pressure distribution is applied on the hole of lug as a boundary condition. The stress intensity factor (SIF) expression for the straight attachment lug with a single through-the-thickness crack, which is subjected an oblique pin-load less than 45 degrees, is determined by studying on the influence law of dimensionless crack length (a/R1)，ratio of outer radius to inside radius (R2/R1), inside radius (R1) and pin-load angle (β) on the SIFs values. The expression is validated by contrasting with the ANSYS results and the data of residual strength test. The stress intensity factor’s amplitude (ΔK) are calculated by the SIF equation to get the values of the Paris constants. The fatigue crack growth model of attachment lug subjected to oblique pin-load is established, offering an analytical as well as experimental method for assessing and designing damage tolerant attachment lugs.

Mechanical Collateral Damage Assessment of Reactor Vessel Bottom Mounted Nozzles: Part II—Analysis and Applications

A comprehensive work scope including the engineering safety assessments, Non-Destructive Examination (NDE) and repair design, is developed by AREVA NP Inc. for the Reactor Vessel (RV) Incore Monitoring Instrument (IMI) nozzles. The joint Bottom Mounted Nozzle (BMN) Assessment Plan is coordinated under the Electric Power Research Institute (EPRI) Materials Reliability Program (MRP). The purpose of such coordination is to produce a safety assessment of consistent scope and methodology to address the different IMI nozzle designs in all U.S. Pressurized Water Reactors (PWRs). The IMI nozzles, which are also referred to as the BMNs are installed in the bottom of the reactor vessel RV. For the Babcock & Wilcox (B&W) designed plants the nozzles consist of the original Alloy 600 nozzle material attached to the reactor vessel by a partial penetration Alloy 182 weld. To increase the resistance of the nozzles against flow induced vibration (FIV), the nozzles were modified, which consisted of a thicker, more rigid Alloy 600 nozzle welded to the RV inside radius surface. Recent industry experience indicates that the Alloy 600 BMNs and their Alloy 82/182 weld metal may be more susceptible to primary water stress corrosion cracking (PWSCC) than previously thought. Although the BMNs have been ranked low in susceptibility to PWSCC, they are ranked as having the most severe consequences of failure. Failure of BMNs represents a scenario that would result in a leak or loss of coolant accident (LOCA). Failure of a BMN was not included in the original design basis for the B&W designed plants. This paper describes the mechanical collateral damage analysis of the BMN engineering safety assessment project performed under the sponsorship of PWR Owner’s Group (PWROG) for the seven operating B&W 177-FA PWR units. Failure of a BMN could potentially lead to pipe whip that could impact other IMI pipes. The goal of the mechanical collateral damage assessment is to determine the potential loads on adjacent IMI pipes. First, the IMI piping configurations for all B&W plants were determined. Based on the piping configurations, potential pipe whip pairs were identified and several representative finite element models of the IMI piping were developed. Using the results of the nonlinear transient dynamic pipe whip analyses, response surfaces were developed, which provided the basis for determining loads due to pipe whip at several different locations. The conservative ultimate capacity analysis corresponding to 50% ultimate strain of the materials showed that the maximum ultimate stress ratio of the intact nozzle cross section at the RV outside radius was acceptable. In addition, the fracture mechanics evaluation of the flawed nozzles, at the RV inside radius, showed that the maximum critical half flaw angle was large enough that early detection of leaking BMNs is possible. For other possible failure modes of the piping, such as the jet impingement, asymmetric cavity pressure effects and insulation frame movement, it was shown that the loads obtained from the pipe whip analyses envelop those loads. The description of this work has been divided into two papers. Part II detailed in this paper presents illustrative examples of the pipe whip analyses and application of response surfaces. Part I [1], to be also presented at PVP-2011, describes the development of the comprehensive collateral damage assessment methodology.

Mechanical Collateral Damage Assessment of Reactor Vessel Bottom Mounted Nozzles: Part I—Requirements and Methodology

A comprehensive work scope including the engineering safety assessments, Non-Destructive Examination (NDE) and repair design, is developed by AREVA NP Inc. for the Reactor Vessel (RV) Incore Monitoring Instrument (IMI) nozzles. The joint Bottom Mounted Nozzle (BMN) Assessment Plan is coordinated under the Electric Power Research Institute (EPRI) Materials Reliability Program (MRP). The purpose of such coordination is to produce a safety assessment of consistent scope and methodology to address the different IMI nozzle designs in all U.S. Pressurized Water Reactors (PWRs). The IMI nozzles, which are also referred to as the BMNs are installed in the bottom of the reactor vessel RV. For the Babcock & Wilcox (B&W) designed plants the nozzles consist of the original Alloy 600 nozzle material attached to the reactor vessel by a partial penetration Alloy 182 weld. To increase the resistance of the nozzles against flow induced vibration (FIV), the nozzles were modified, which consisted of a thicker, more rigid Alloy 600 nozzle welded to the RV inside radius surface. Recent industry experience indicates that the Alloy 600 BMNs and their Alloy 82/182 weld metal may be more susceptible to primary water stress corrosion cracking (PWSCC) than previously thought. Although the BMNs have been ranked low in susceptibility to PWSCC, they are ranked as having the most severe consequences of failure. Failure of BMNs represents a scenario that would result in a leak or loss of coolant accident (LOCA). Failure of a BMN was not included in the original design basis for the B&W designed plants. This paper describes the mechanical collateral damage analysis of the BMN engineering safety assessment project performed under the sponsorship of PWR Owner’s Group (PWROG) for the seven operating B&W 177-FA PWR units. Failure of a BMN could potentially lead to pipe whip that could impact other IMI pipes. The goal of the mechanical collateral damage assessment is to determine the potential loads on adjacent IMI pipes. First, the IMI piping configurations for all B&W plants were determined. Based on the piping configurations, potential pipe whip pairs were identified and several representative finite element models of the IMI piping were developed. Using the results of the nonlinear transient dynamic pipe whip analyses, response surfaces were developed, which provided the basis for determining loads due to pipe whip at several different locations. The conservative ultimate capacity analysis corresponding to 50% ultimate strain of the materials showed that the maximum ultimate stress ratio of the intact nozzle cross section at the RV outside radius was acceptable. In addition, the fracture mechanics evaluation of the flawed nozzles, at the RV inside radius, showed that the maximum critical half flaw angle was large enough that early detection of leaking BMNs is possible. For other possible failure modes of the piping, such as the jet impingement, asymmetric cavity pressure effects and insulation frame movement, it was shown that the loads obtained from the pipe whip analyses envelop those loads. The description of this work has been divided into two papers. Part I, detailed in this paper, describes the development of the comprehensive collateral damage assessment methodology. Part II, [1], to be also presented at PVP-2011, presents illustrative examples of the pipe whip analyses and application of response surfaces.