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	tAdded bond breaking - sphere - GPU-based 3D discrete element method algorithm …
	git clone git://src.adamsgaard.dk/sphere
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	---
	commit ecfc70812628f9ac56ab817087ad15778ac88c88
	parent 3b2d08a037d933e278e3c0caf736feb8f1e54b9b
	Author: Anders Damsgaard <[email protected]>
	Date: Tue, 12 Mar 2013 21:12:46 +0100

	Added bond breaking

	Diffstat:
	M src/cohesion.cuh \| 20 ++++++++++++++++++++
	M src/datatypes.h \| 2 ++
	M src/file_io.cpp \| 4 ++++

	3 files changed, 26 insertions(+), 0 deletions(-)
	---
	diff --git a/src/cohesion.cuh b/src/cohesion.cuh
	t@@ -191,6 +191,26 @@ __global__ void bondsLinear(
	//const Float3 t_i = t_n - t_t; //t_n - t_t;
	//const Float3 t_j = t_n + t_t;

	+
	+ //// Bond strength (Potyondy & Cundall 2004)
	+ // Extensions of Euler-Bernoulli beam bending theory
	+ // Max. stresses in bond periphery
	+
	+ // Tensile stress
	+ const Float sigma_max = length(f_n) / A + length(t_t) * R_bar / I;
	+
	+ // Shear stress
	+ const Float tau_max = length(f_t) / A + length(t_n) * R_bar / J;
	+
	+ // Break bond if tensile and shear stresses exceed strengths
	+ if (sigma_max >= devC_params.sigma_b \|\| tau_max >= devC_params.tau_b) {
	+ __syncthreads();
	+ dev_bonds[idx].x = devC_params.nb0;
	+ return;
	+ }
	+
	+
	+
	//// Save values
	__syncthreads();

	diff --git a/src/datatypes.h b/src/datatypes.h
	t@@ -92,6 +92,8 @@ struct Params {
	Float V_b; // Volume of fluid in capillary bond
	Float lambda_bar; // Radius multiplier to parallel-bond radii
	unsigned int nb0; // Number of inter-particle bonds at t=0
	+ Float sigma_b; // Bond tensile strength
	+ Float tau_b; // Bond shear strength
	};

	// Structure containing wall parameters
	diff --git a/src/file_io.cpp b/src/file_io.cpp
	t@@ -208,6 +208,8 @@ void DEM::readbin(const char *target)
	// Read bond parameters
	ifs.read(as_bytes(params.lambda_bar), sizeof(params.lambda_bar));
	ifs.read(as_bytes(params.nb0), sizeof(params.nb0));
	+ ifs.read(as_bytes(params.sigma_b), sizeof(params.sigma_b));
	+ ifs.read(as_bytes(params.tau_b), sizeof(params.tau_b));
	k.bonds = new uint2[params.nb0];
	k.bonds_delta = new Float4[np];
	k.bonds_omega = new Float4[np];
	t@@ -365,6 +367,8 @@ void DEM::writebin(const char *target)
	// Write bond parameters
	ofs.write(as_bytes(params.lambda_bar), sizeof(params.lambda_bar));
	ofs.write(as_bytes(params.nb0), sizeof(params.nb0));
	+ ofs.write(as_bytes(params.sigma_b), sizeof(params.sigma_b));
	+ ofs.write(as_bytes(params.tau_b), sizeof(params.tau_b));
	for (i = 0; i<params.nb0; ++i) {
	ofs.write(as_bytes(k.bonds[i].x), sizeof(unsigned int));
	ofs.write(as_bytes(k.bonds[i].y), sizeof(unsigned int));