A Novel Attribute-Based Encryption Approach with Integrity Verification for CAD Assembly Models

Cloud manufacturing is one of the three key technologies that enable intelligent manufacturing.This paper presents a novel attribute-based encryption(ABE)approach for computer-aided design(CAD)assembly models to effectively support hierarchical access control,integrity verification,and deformation protection for co-design scenarios in cloud manufacturing.An assembly hierarchy access tree(AHAT)is designed as the hierarchical access structure.Attribute-related ciphertext elements,which are contained in an assembly ciphertext(ACT)file,are adapted for content keys decryption instead of CAD component files.We modify the original Merkle tree(MT)and reconstruct an assembly MT.The proposed ABE framework has the ability to combine the deformation protection method with a content privacy of CAD models.The proposed encryption scheme is demonstrated to be secure under the standard assumption.Experimental simulation on typical CAD assembly models demonstrates that the proposed approach is feasible in applications.

Application Research of assembly line modeling based on Time Petri Net

With the continuous progress of manufacturing industry,automatic assembly line has become a very mature production mode in modern factories,and the quality of assembly line design has become an important issue related to the development of manufacturing enterprises.In this paper,a graphical model based on Petri Net is established for the first full load time of the assembly line.The accessibility of the P/T system and the production rhythm of the assembly line are calculated by computer simulation.Finally,according to the simulation model,an experimental platform is built to verify the rationality of the model.Experimental results show that the model can accurately express the equipment allocation process of assembly line.

Solving Level Scheduling in Mixed Model Assembly Line by Simulated Annealing Method

This paper presents an application of the simulated annealing algorithm to solve level schedules in mixed model assembly line. Solving production sequences with both number of setups and material usage rates to the minimum rate will optimize the level schedule. Miltenburg algorithm (1989) is first used to get seed sequence to optimize further. For this the utility time of the line and setup time requirement on each station is considered. This seed sequence is optimized by simulated annealing. This investigation helps to understand the importance of utility in the assembly line. Up to 15 product sequences are taken and constructed by using randomizing method and find the objective function value for this. For a sequence optimization, a meta-heuristic seems much more promising to guide the search into feasible regions of the solution space. Simulated annealing is a stochastic local search meta-heuristic, which bases the acceptance of a modified neighboring solution on a probabilistic scheme inspired by thermal processes for obtaining low-energy states in heat baths. Experimental results show that the simulated annealing approach is favorable and competitive compared to Miltenburg’s constructive algorithm for the problems set considered. It is proposed to found 16,985 solutions, the time taken for computation is 23.47 to 130.35, and the simulated annealing improves 49.33% than Miltenberg.

USING LOGIC COMPONENTS FOR CONCEPTUAL DIE DESIGN

Logic components are used to support the conceptual design Taking the stamping die structure as the research object,several logic components are defined for the conceptual die construction design A new method logic assembly modeling is presented to satisfy the characteristic of the top down die design process Representing shapes and spatial relations in logic can provide a natural,intuitive method of developing complete computer systems for reasoning about die construction design at the conceptual stage This method can reflect the designer’s thought clearly and provide the designer with a test bed for generating alternatives and performing reasoning work at the conceptual die design

An Elasto-plastic Damage Constitutive Theory Based on Pair Functional Potentials and Slip Mechanism

The deformation work rate can be expressed by the time rate of pair functional potentials which describe the energy of materials in terms of atomic bonds and atom embedding interactions.According to Cauchy-Born rule,the relations between the microscopic deformations of atomic bonds and electron gas and macroscopic deformation are established.Further,atomic bonds are grouped according to their directions,and atomic bonds in the same direction are simplified as a spring-bundle component.Atom embedding interactions in unit reference volume are simplified as a cubage component.Consequently,a material model composed of spring-bundle components and a cubage component is established.Since the essence of damage is the decrease and loss of atomic bonding forces,the damage effect can be reflected by the response functions of these two kinds of components.Formulating the mechanical responses of two kinds of components,the corresponding elasto-damage constitutive equations are derived.Considering that slip is the main plastic deformation mechanism of polycrystalline metals,the slip systems of crystal are extended to polycrystalline,and the slip components are proposed to describe the plastic deformation.Based on the decomposition of deformation gradient and combining the plastic response with the elasto-damage one,the elasto-plastic damage constitutive equations are derived.As a result,a material model formulated with spring-bundle components,a cubage component and slip components is established.Different from phenomenological constitutive theories,the mechanical property of materials depends on the property of components rather than that directly obtained on the representative volume element.The effect of finite deformation is taken into account in this model.Parameter calibration procedure and the basic characteristics of this model are discussed.