Modified differential evolution algorithm for simple assembly line balancing with a limit on the number of machine types

This article proposes the differential evolution algorithm (DE) and the modified differential evolution algorithm (DE-C) to solve a simple assembly line balancing problem type 1 (SALBP-1) and SALBP-1 when the maximum number of machine types in a workstation is considered (SALBP-1M). The proposed algorithms are tested and compared with existing effective heuristics using various sets of test instances found in the literature. The computational results show that the proposed heuristics is one of the best methods, compared with the other approaches.     

A MAX-MIN ant system for unconstrained multi-level lot-sizing problems

In this paper, we present an ant-based algorithm for solving unconstrained multi-level lot-sizing problems called ant system for multi-level lot-sizing algorithm (ASMLLS). We apply a hybrid approach where we use ant colony optimization in order to find a good lot-sizing sequence, i.e. a sequence of the different items in the product structure in which we apply a modified Wagner–Whitin algorithm for each item separately. Based on the setup costs each ant generates a sequence of items. Afterwards a simple single-stage lot-sizing rule is applied with modified setup costs. This modification of the setup costs depends on the position of the item in the lot-sizing sequence, on the items which have been lot-sized before, and on two further parameters, which are tried to be improved by a systematic search. For small-sized problems ASMLLS is among the best algorithms, but for most medium- and large-sized problems it outperforms all other approaches regarding solution quality as well as computational time.     

MOLECULAR DYNAMICS SIMULATION OF NANOMETRIC CUTTING

Molecular Dynamics (MD) simulations of nanometric cutting of single-crystal copper were conducted to predict cutting forces and investigate the mechanism of chip formation at the nano-level. The MD simulations were conducted at a conventional cutting speed of 5 m/s and different depths of cut (0.724–2.172 nm), and cutting forces and shear angle were predicted. The effect of tool rake angles and depths of cut on the mechanism of chip formation was investigated. Tools with different rake angles, namely 0°, 5°, 10°, 15°, 30°, and 45°, were used. It was found that the cutting force, thrust force, and the ratio of the thrust force to cutting force decrease with increasing rake angle. However, the ratio of the thrust force to the cutting force is found to be independent of the depth of cut. In addition, the chip thickness was found to decrease with an increase in rake angle. As a consequence, the cutting ratio and the shear angle increase as the rake angle increases. The dislocation and subsurface deformation in the workpiece material were observed in the cutting region near the tool rake face. The adhesion of copper atoms to the diamond tool was clearly seen. The same approach can be used to simulate micromachining by significantly increasing the number of atoms in the MD model to represent cutting depths in the order of microns.